The present invention relates to a dental appliance and a process for making a dental appliance and, in particular, relates to a laminated flexible dental appliance and a process for making a laminated flexible dental appliance.
For many years the dental industry has produced rigid dental appliances, such as dentures, and attempted to achieve a comfortable yet snug fit of the appliances in patients' mouths. Conventional rigid dental appliances do not address day to day changes of oral tissues. For a typical wearer, this shortcoming results in minor but daily irritation and discomfort.
Desired fit and comfort have often been elusive and far too many dental appliances undesirably shift while being worn. This shifting is uncomfortable and disconcerting to patients. In extreme cases, poorly fitting dental appliances may cause ulcers in a patient's mouth. The problem is particularly serious in patients whose dental tissues (especially the gums) include an undercut region.
An undercut region of the gum generally fails to interact with and support a typical rigid dental appliance. This is due to the rigid design of typical dental appliances, which are normally constructed of acrylic. More specifically, because typical dental appliances are rigid, they can not be installed over a patient's gums and still curve inward to fit snuggly against the undercut region of the gum. In use, particularly when biting or chewing, the typical rigid dental appliance sits atop the undercut gum and tends to rock back and forth upon the rounded extreme edge of the gum, with its skirt moving into and out of the undercut region. The rigid opposite opposing skirt also follows the rocking action, whether or not the opposite gum surface has an undercut. Such rocking action is an irritation to the patient and potentially detrimental to the patient's gum tissue and bone adjacent the undercut region.
An additional challenge in dental appliances is to provide dental appliances which are comfortable to a patient. Two prior art approaches to attempt to improve comfort are to improve the fit of the dental appliance and to provide a soft liner. Alternative approaches have been to prepare dental appliances with hinges or to prepare flexible dental appliances employing nylon. While flexible nylon dental appliances might appear to be a promising solution, nylon flexible dental appliances are difficult or even impossible to repair and adjust. The nylon appliances are typically limited to about 1.5 to 2 mm in thickness because thicker nylon appliances are often excessively stiff or even rigid. This in turn means that nylon appliances fail to address the problems of filling in or compensating for destroyed or missing gum tissues, a condition often encountered in patients who have lost a few millimeters to several centimeters of bone and gum tissue to oral cancer surgery. Additionally, instead of rocking on the gum, the flexible nature of the prior art flexible dental appliances undesirably allowed the attached artificial teeth to flex more than desired by most patients. Other prior art attempts at preparing "soft" dental appliances have also been unacceptable due to insufficient strength or durability.
Silicone soft liners have also been tried as a means of improving comfort and fit for dental appliances. However, silicone soft liners are characterized by unacceptable low durability and difficulty in preparation and processing. Silicone soft liners are also porous. Porosity is undesirable because it tends to support micro-organisms, such as bacterial or fungal growths, which in turn generate undesirable tastes and odors as well as additional health challenges for the patient. Soft liners used against acrylic dental appliances are compressible and must rely solely upon the acrylic appliance for strength. If the acrylic appliance portion is too thin, the acrylic will crack when the soft layer is compressed. Typically, the acrylic portion needs to be 3 mm or more in thickness to avoid cracking. Hinges between separate acrylic portions have even been employed to attempt to address these problems. Additionally, the soft liners presently available to the industry do not bond directly to the acrylic, further complicating production and durability problems.
Patients would appreciate a comfortable dental appliance which is strong and durable, installs easily, fits well once installed by closely fitting against any undercut regions, and yet holds artificial teeth firmly in a preselected position relative to the patient's gums. The present invention includes a dental appliance and a process for preparing a dental appliance which addresses these challenges. The materials employed are closed cell materials to discourage micro-organism growth.